# Copyright (c) 2010 Cloud.com, Inc
# Copyright 2012 Cloudbase Solutions Srl
# All Rights Reserved.
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.

"""
Management class for basic VM operations.
"""
import functools
import os
import time

from eventlet import timeout as etimeout
from os_win import constants as os_win_const
from os_win import exceptions as os_win_exc
from os_win import utilsfactory
from oslo_concurrency import processutils
from oslo_log import log as logging
from oslo_service import loopingcall
from oslo_utils import excutils
from oslo_utils import fileutils
from oslo_utils import importutils
from oslo_utils import units
from oslo_utils import uuidutils

from nova.api.metadata import base as instance_metadata
from nova.compute import vm_states
import nova.conf
from nova import exception
from nova.i18n import _, _LI, _LE, _LW
from nova import objects
from nova import utils
from nova.virt import configdrive
from nova.virt import hardware
from nova.virt.hyperv import block_device_manager
from nova.virt.hyperv import constants
from nova.virt.hyperv import imagecache
from nova.virt.hyperv import pathutils
from nova.virt.hyperv import serialconsoleops
from nova.virt.hyperv import volumeops

LOG = logging.getLogger(__name__)


CONF = nova.conf.CONF

SHUTDOWN_TIME_INCREMENT = 5
REBOOT_TYPE_SOFT = 'SOFT'
REBOOT_TYPE_HARD = 'HARD'

VM_GENERATIONS = {
    constants.IMAGE_PROP_VM_GEN_1: constants.VM_GEN_1,
    constants.IMAGE_PROP_VM_GEN_2: constants.VM_GEN_2
}

VM_GENERATIONS_CONTROLLER_TYPES = {
    constants.VM_GEN_1: constants.CTRL_TYPE_IDE,
    constants.VM_GEN_2: constants.CTRL_TYPE_SCSI
}


def check_admin_permissions(function):
    @functools.wraps(function)
    def wrapper(self, *args, **kwds):

        # Make sure the windows account has the required admin permissions.
        self._vmutils.check_admin_permissions()
        return function(self, *args, **kwds)
    return wrapper

NEUTRON_VIF_DRIVER = 'nova.virt.hyperv.vif.HyperVNeutronVIFDriver'
NOVA_VIF_DRIVER = 'nova.virt.hyperv.vif.HyperVNovaNetworkVIFDriver'


def get_network_driver():
    """"Return the correct network module"""
    if nova.network.is_neutron():
        return NEUTRON_VIF_DRIVER
    else:
        return NOVA_VIF_DRIVER


class VMOps(object):
    # The console log is stored in two files, each should have at most half of
    # the maximum console log size.
    _MAX_CONSOLE_LOG_FILE_SIZE = units.Mi / 2
    _ROOT_DISK_CTRL_ADDR = 0

    def __init__(self):
        self._vmutils = utilsfactory.get_vmutils()
        self._metricsutils = utilsfactory.get_metricsutils()
        self._vhdutils = utilsfactory.get_vhdutils()
        self._hostutils = utilsfactory.get_hostutils()
        self._pathutils = pathutils.PathUtils()
        self._volumeops = volumeops.VolumeOps()
        self._imagecache = imagecache.ImageCache()
        self._serial_console_ops = serialconsoleops.SerialConsoleOps()
        self._block_dev_man = (
            block_device_manager.BlockDeviceInfoManager())
        self._vif_driver = None
        self._load_vif_driver_class()

    def _load_vif_driver_class(self):
        class_name = get_network_driver()
        self._vif_driver = importutils.import_object(class_name)

    def list_instance_uuids(self):
        instance_uuids = []
        for (instance_name, notes) in self._vmutils.list_instance_notes():
            if notes and uuidutils.is_uuid_like(notes[0]):
                instance_uuids.append(str(notes[0]))
            else:
                LOG.debug("Notes not found or not resembling a GUID for "
                          "instance: %s", instance_name)
        return instance_uuids

    def list_instances(self):
        return self._vmutils.list_instances()

    def estimate_instance_overhead(self, instance_info):
        # NOTE(claudiub): When an instance starts, Hyper-V creates a VM memory
        # file on the local disk. The file size is the same as the VM's amount
        # of memory. Since disk_gb must be an integer, and memory is MB, round
        # up from X512 MB.
        return {'memory_mb': 0,
                'disk_gb': (instance_info['memory_mb'] + 512) // units.Ki}

    def get_info(self, instance):
        """Get information about the VM."""
        LOG.debug("get_info called for instance", instance=instance)

        instance_name = instance.name
        if not self._vmutils.vm_exists(instance_name):
            raise exception.InstanceNotFound(instance_id=instance.uuid)

        info = self._vmutils.get_vm_summary_info(instance_name)

        state = constants.HYPERV_POWER_STATE[info['EnabledState']]
        return hardware.InstanceInfo(state=state,
                                     max_mem_kb=info['MemoryUsage'],
                                     mem_kb=info['MemoryUsage'],
                                     num_cpu=info['NumberOfProcessors'],
                                     cpu_time_ns=info['UpTime'])

    def _create_root_device(self, context, instance, root_disk_info, vm_gen):
        path = None
        if root_disk_info['type'] == constants.DISK:
            path = self._create_root_vhd(context, instance)
            self.check_vm_image_type(instance.uuid, vm_gen, path)
        root_disk_info['path'] = path

    def _create_root_vhd(self, context, instance, rescue_image_id=None):
        is_rescue_vhd = rescue_image_id is not None

        base_vhd_path = self._imagecache.get_cached_image(context, instance,
                                                          rescue_image_id)
        base_vhd_info = self._vhdutils.get_vhd_info(base_vhd_path)
        base_vhd_size = base_vhd_info['VirtualSize']
        format_ext = base_vhd_path.split('.')[-1]
        root_vhd_path = self._pathutils.get_root_vhd_path(instance.name,
                                                          format_ext,
                                                          is_rescue_vhd)
        root_vhd_size = instance.flavor.root_gb * units.Gi

        try:
            if CONF.use_cow_images:
                LOG.debug("Creating differencing VHD. Parent: "
                          "%(base_vhd_path)s, Target: %(root_vhd_path)s",
                          {'base_vhd_path': base_vhd_path,
                           'root_vhd_path': root_vhd_path},
                          instance=instance)
                self._vhdutils.create_differencing_vhd(root_vhd_path,
                                                       base_vhd_path)
                vhd_type = self._vhdutils.get_vhd_format(base_vhd_path)
                if vhd_type == constants.DISK_FORMAT_VHD:
                    # The base image has already been resized. As differencing
                    # vhdx images support it, the root image will be resized
                    # instead if needed.
                    return root_vhd_path
            else:
                LOG.debug("Copying VHD image %(base_vhd_path)s to target: "
                          "%(root_vhd_path)s",
                          {'base_vhd_path': base_vhd_path,
                           'root_vhd_path': root_vhd_path},
                          instance=instance)
                self._pathutils.copyfile(base_vhd_path, root_vhd_path)

            root_vhd_internal_size = (
                self._vhdutils.get_internal_vhd_size_by_file_size(
                    base_vhd_path, root_vhd_size))

            if not is_rescue_vhd and self._is_resize_needed(
                    root_vhd_path, base_vhd_size,
                    root_vhd_internal_size, instance):
                self._vhdutils.resize_vhd(root_vhd_path,
                                          root_vhd_internal_size,
                                          is_file_max_size=False)
        except Exception:
            with excutils.save_and_reraise_exception():
                if self._pathutils.exists(root_vhd_path):
                    self._pathutils.remove(root_vhd_path)

        return root_vhd_path

    def _is_resize_needed(self, vhd_path, old_size, new_size, instance):
        if new_size < old_size:
            raise exception.FlavorDiskSmallerThanImage(
                flavor_size=new_size, image_size=old_size)
        elif new_size > old_size:
            LOG.debug("Resizing VHD %(vhd_path)s to new "
                      "size %(new_size)s",
                      {'new_size': new_size,
                       'vhd_path': vhd_path},
                      instance=instance)
            return True
        return False

    def _create_ephemerals(self, instance, ephemerals):
        for index, eph in enumerate(ephemerals):
            eph['format'] = self._vhdutils.get_best_supported_vhd_format()
            eph_name = "eph%s" % index
            eph['path'] = self._pathutils.get_ephemeral_vhd_path(
                instance.name, eph['format'], eph_name)
            self.create_ephemeral_disk(instance.name, eph)

    def create_ephemeral_disk(self, instance_name, eph_info):
        self._vhdutils.create_dynamic_vhd(eph_info['path'],
                                          eph_info['size'] * units.Gi)

    @staticmethod
    def _get_vif_metadata(context, instance_id):
        vifs = objects.VirtualInterfaceList.get_by_instance_uuid(context,
                                                                 instance_id)
        vif_metadata = []
        for vif in vifs:
            if 'tag' in vif and vif.tag:
                device = objects.NetworkInterfaceMetadata(
                    mac=vif.address,
                    bus=objects.PCIDeviceBus(),
                    tags=[vif.tag])
                vif_metadata.append(device)

        return vif_metadata

    def _save_device_metadata(self, context, instance, block_device_info):
        """Builds a metadata object for instance devices, that maps the user
           provided tag to the hypervisor assigned device address.
        """
        metadata = []

        metadata.extend(self._get_vif_metadata(context, instance.uuid))
        if block_device_info:
            metadata.extend(self._block_dev_man.get_bdm_metadata(
                context, instance, block_device_info))

        if metadata:
            instance.device_metadata = objects.InstanceDeviceMetadata(
                devices=metadata)

    @check_admin_permissions
    def spawn(self, context, instance, image_meta, injected_files,
              admin_password, network_info, block_device_info=None):
        """Create a new VM and start it."""
        LOG.info(_LI("Spawning new instance"), instance=instance)

        instance_name = instance.name
        if self._vmutils.vm_exists(instance_name):
            raise exception.InstanceExists(name=instance_name)

        # Make sure we're starting with a clean slate.
        self._delete_disk_files(instance_name)

        vm_gen = self.get_image_vm_generation(instance.uuid, image_meta)

        self._block_dev_man.validate_and_update_bdi(
            instance, image_meta, vm_gen, block_device_info)
        root_device = block_device_info['root_disk']
        self._create_root_device(context, instance, root_device, vm_gen)
        self._create_ephemerals(instance, block_device_info['ephemerals'])

        try:
            self.create_instance(instance, network_info, root_device,
                                 block_device_info, vm_gen)
            self._save_device_metadata(context, instance, block_device_info)

            if configdrive.required_by(instance):
                configdrive_path = self._create_config_drive(context,
                                                             instance,
                                                             injected_files,
                                                             admin_password,
                                                             network_info)

                self.attach_config_drive(instance, configdrive_path, vm_gen)

            self.power_on(instance)
        except Exception:
            with excutils.save_and_reraise_exception():
                self.destroy(instance)

    def create_instance(self, instance, network_info, root_device,
                        block_device_info, vm_gen):
        instance_name = instance.name
        instance_path = os.path.join(CONF.instances_path, instance_name)

        self._vmutils.create_vm(instance_name,
                                instance.flavor.memory_mb,
                                instance.flavor.vcpus,
                                CONF.hyperv.limit_cpu_features,
                                CONF.hyperv.dynamic_memory_ratio,
                                vm_gen,
                                instance_path,
                                [instance.uuid])

        self._configure_remotefx(instance, vm_gen)

        self._vmutils.create_scsi_controller(instance_name)
        self._attach_root_device(instance_name, root_device)
        self._attach_ephemerals(instance_name, block_device_info['ephemerals'])
        self._volumeops.attach_volumes(
            block_device_info['block_device_mapping'], instance_name)

        # For the moment, we use COM port 1 when getting the serial console
        # log as well as interactive sessions. In the future, the way in which
        # we consume instance serial ports may become configurable.
        #
        # Note that Hyper-V instances will always have 2 COM ports
        serial_ports = {
            constants.DEFAULT_SERIAL_CONSOLE_PORT:
                constants.SERIAL_PORT_TYPE_RW}
        self._create_vm_com_port_pipes(instance, serial_ports)

        for vif in network_info:
            LOG.debug('Creating nic for instance', instance=instance)
            self._vmutils.create_nic(instance_name,
                                     vif['id'],
                                     vif['address'])
            self._vif_driver.plug(instance, vif)

        if CONF.hyperv.enable_instance_metrics_collection:
            self._metricsutils.enable_vm_metrics_collection(instance_name)

    def _configure_remotefx(self, instance, vm_gen):
        extra_specs = instance.flavor.extra_specs
        remotefx_max_resolution = extra_specs.get(
            constants.FLAVOR_ESPEC_REMOTEFX_RES)
        if not remotefx_max_resolution:
            # RemoteFX not required.
            return

        if not CONF.hyperv.enable_remotefx:
            raise exception.InstanceUnacceptable(
                _("enable_remotefx configuration option needs to be set to "
                  "True in order to use RemoteFX."))

        if not self._hostutils.check_server_feature(
                self._hostutils.FEATURE_RDS_VIRTUALIZATION):
            raise exception.InstanceUnacceptable(
                _("The RDS-Virtualization feature must be installed in order "
                  "to use RemoteFX."))

        if not self._vmutils.vm_gen_supports_remotefx(vm_gen):
            raise exception.InstanceUnacceptable(
                _("RemoteFX is not supported on generation %s virtual "
                  "machines on this version of Windows.") % vm_gen)

        instance_name = instance.name
        LOG.debug('Configuring RemoteFX for instance: %s', instance_name)

        remotefx_monitor_count = int(extra_specs.get(
            constants.FLAVOR_ESPEC_REMOTEFX_MONITORS) or 1)
        remotefx_vram = extra_specs.get(
            constants.FLAVOR_ESPEC_REMOTEFX_VRAM)
        vram_bytes = int(remotefx_vram) * units.Mi if remotefx_vram else None

        self._vmutils.enable_remotefx_video_adapter(
            instance_name,
            remotefx_monitor_count,
            remotefx_max_resolution,
            vram_bytes)

    def _attach_root_device(self, instance_name, root_dev_info):
        if root_dev_info['type'] == constants.VOLUME:
            self._volumeops.attach_volume(root_dev_info['connection_info'],
                                          instance_name,
                                          disk_bus=root_dev_info['disk_bus'])
        else:
            self._attach_drive(instance_name, root_dev_info['path'],
                               root_dev_info['drive_addr'],
                               root_dev_info['ctrl_disk_addr'],
                               root_dev_info['disk_bus'],
                               root_dev_info['type'])

    def _attach_ephemerals(self, instance_name, ephemerals):
        for eph in ephemerals:
            # if an ephemeral doesn't have a path, it might have been removed
            # during resize.
            if eph.get('path'):
                self._attach_drive(
                    instance_name, eph['path'], eph['drive_addr'],
                    eph['ctrl_disk_addr'], eph['disk_bus'],
                    constants.BDI_DEVICE_TYPE_TO_DRIVE_TYPE[
                        eph['device_type']])

    def _attach_drive(self, instance_name, path, drive_addr, ctrl_disk_addr,
                      controller_type, drive_type=constants.DISK):
        if controller_type == constants.CTRL_TYPE_SCSI:
            self._vmutils.attach_scsi_drive(instance_name, path, drive_type)
        else:
            self._vmutils.attach_ide_drive(instance_name, path, drive_addr,
                                           ctrl_disk_addr, drive_type)

    def get_image_vm_generation(self, instance_id, image_meta):
        default_vm_gen = self._hostutils.get_default_vm_generation()
        image_prop_vm = image_meta.properties.get('hw_machine_type',
                                                  default_vm_gen)
        if image_prop_vm not in self._hostutils.get_supported_vm_types():
            reason = _LE('Requested VM Generation %s is not supported on '
                         'this OS.') % image_prop_vm
            raise exception.InstanceUnacceptable(instance_id=instance_id,
                                                 reason=reason)

        return VM_GENERATIONS[image_prop_vm]

    def check_vm_image_type(self, instance_id, vm_gen, root_vhd_path):
        if (vm_gen != constants.VM_GEN_1 and root_vhd_path and
                self._vhdutils.get_vhd_format(
                    root_vhd_path) == constants.DISK_FORMAT_VHD):
            reason = _LE('Requested VM Generation %s, but provided VHD '
                         'instead of VHDX.') % vm_gen
            raise exception.InstanceUnacceptable(instance_id=instance_id,
                                                 reason=reason)

    def _create_config_drive(self, context, instance, injected_files,
                             admin_password, network_info, rescue=False):
        if CONF.config_drive_format != 'iso9660':
            raise exception.ConfigDriveUnsupportedFormat(
                format=CONF.config_drive_format)

        LOG.info(_LI('Using config drive for instance'), instance=instance)

        extra_md = {}
        if admin_password and CONF.hyperv.config_drive_inject_password:
            extra_md['admin_pass'] = admin_password

        inst_md = instance_metadata.InstanceMetadata(
                      instance, content=injected_files, extra_md=extra_md,
                      network_info=network_info, request_context=context)

        configdrive_path_iso = self._pathutils.get_configdrive_path(
            instance.name, constants.DVD_FORMAT, rescue=rescue)
        LOG.info(_LI('Creating config drive at %(path)s'),
                 {'path': configdrive_path_iso}, instance=instance)

        with configdrive.ConfigDriveBuilder(instance_md=inst_md) as cdb:
            try:
                cdb.make_drive(configdrive_path_iso)
            except processutils.ProcessExecutionError as e:
                with excutils.save_and_reraise_exception():
                    LOG.error(_LE('Creating config drive failed with '
                                  'error: %s'),
                              e, instance=instance)

        if not CONF.hyperv.config_drive_cdrom:
            configdrive_path = self._pathutils.get_configdrive_path(
                instance.name, constants.DISK_FORMAT_VHD, rescue=rescue)
            utils.execute(CONF.hyperv.qemu_img_cmd,
                          'convert',
                          '-f',
                          'raw',
                          '-O',
                          'vpc',
                          configdrive_path_iso,
                          configdrive_path,
                          attempts=1)
            self._pathutils.remove(configdrive_path_iso)
        else:
            configdrive_path = configdrive_path_iso

        return configdrive_path

    def attach_config_drive(self, instance, configdrive_path, vm_gen):
        configdrive_ext = configdrive_path[(configdrive_path.rfind('.') + 1):]
        # Do the attach here and if there is a certain file format that isn't
        # supported in constants.DISK_FORMAT_MAP then bomb out.
        try:
            drive_type = constants.DISK_FORMAT_MAP[configdrive_ext]
            controller_type = VM_GENERATIONS_CONTROLLER_TYPES[vm_gen]
            self._attach_drive(instance.name, configdrive_path, 1, 0,
                               controller_type, drive_type)
        except KeyError:
            raise exception.InvalidDiskFormat(disk_format=configdrive_ext)

    def _detach_config_drive(self, instance_name, rescue=False, delete=False):
        configdrive_path = self._pathutils.lookup_configdrive_path(
            instance_name, rescue=rescue)

        if configdrive_path:
            self._vmutils.detach_vm_disk(instance_name,
                                         configdrive_path,
                                         is_physical=False)
            if delete:
                self._pathutils.remove(configdrive_path)

    def _delete_disk_files(self, instance_name):
        self._pathutils.get_instance_dir(instance_name,
                                         create_dir=False,
                                         remove_dir=True)

    def destroy(self, instance, network_info=None, block_device_info=None,
                destroy_disks=True):
        instance_name = instance.name
        LOG.info(_LI("Got request to destroy instance"), instance=instance)
        try:
            if self._vmutils.vm_exists(instance_name):

                # Stop the VM first.
                self._vmutils.stop_vm_jobs(instance_name)
                self.power_off(instance)

                if network_info:
                    for vif in network_info:
                        self._vif_driver.unplug(instance, vif)

                self._vmutils.destroy_vm(instance_name)
                self._volumeops.disconnect_volumes(block_device_info)
            else:
                LOG.debug("Instance not found", instance=instance)

            if destroy_disks:
                self._delete_disk_files(instance_name)
        except Exception:
            with excutils.save_and_reraise_exception():
                LOG.exception(_LE('Failed to destroy instance: %s'),
                              instance_name)

    def reboot(self, instance, network_info, reboot_type):
        """Reboot the specified instance."""
        LOG.debug("Rebooting instance", instance=instance)

        if reboot_type == REBOOT_TYPE_SOFT:
            if self._soft_shutdown(instance):
                self.power_on(instance)
                return

        self._set_vm_state(instance,
                           os_win_const.HYPERV_VM_STATE_REBOOT)

    def _soft_shutdown(self, instance,
                       timeout=CONF.hyperv.wait_soft_reboot_seconds,
                       retry_interval=SHUTDOWN_TIME_INCREMENT):
        """Perform a soft shutdown on the VM.

           :return: True if the instance was shutdown within time limit,
                    False otherwise.
        """
        LOG.debug("Performing Soft shutdown on instance", instance=instance)

        while timeout > 0:
            # Perform a soft shutdown on the instance.
            # Wait maximum timeout for the instance to be shutdown.
            # If it was not shutdown, retry until it succeeds or a maximum of
            # time waited is equal to timeout.
            wait_time = min(retry_interval, timeout)
            try:
                LOG.debug("Soft shutdown instance, timeout remaining: %d",
                          timeout, instance=instance)
                self._vmutils.soft_shutdown_vm(instance.name)
                if self._wait_for_power_off(instance.name, wait_time):
                    LOG.info(_LI("Soft shutdown succeeded."),
                             instance=instance)
                    return True
            except os_win_exc.HyperVException as e:
                # Exception is raised when trying to shutdown the instance
                # while it is still booting.
                LOG.debug("Soft shutdown failed: %s", e, instance=instance)
                time.sleep(wait_time)

            timeout -= retry_interval

        LOG.warning(_LW("Timed out while waiting for soft shutdown."),
                    instance=instance)
        return False

    def pause(self, instance):
        """Pause VM instance."""
        LOG.debug("Pause instance", instance=instance)
        self._set_vm_state(instance,
                           os_win_const.HYPERV_VM_STATE_PAUSED)

    def unpause(self, instance):
        """Unpause paused VM instance."""
        LOG.debug("Unpause instance", instance=instance)
        self._set_vm_state(instance,
                           os_win_const.HYPERV_VM_STATE_ENABLED)

    def suspend(self, instance):
        """Suspend the specified instance."""
        LOG.debug("Suspend instance", instance=instance)
        self._set_vm_state(instance,
                           os_win_const.HYPERV_VM_STATE_SUSPENDED)

    def resume(self, instance):
        """Resume the suspended VM instance."""
        LOG.debug("Resume instance", instance=instance)
        self._set_vm_state(instance,
                           os_win_const.HYPERV_VM_STATE_ENABLED)

    def power_off(self, instance, timeout=0, retry_interval=0):
        """Power off the specified instance."""
        LOG.debug("Power off instance", instance=instance)

        # We must make sure that the console log workers are stopped,
        # otherwise we won't be able to delete or move the VM log files.
        self._serial_console_ops.stop_console_handler(instance.name)

        if retry_interval <= 0:
            retry_interval = SHUTDOWN_TIME_INCREMENT

        try:
            if timeout and self._soft_shutdown(instance,
                                               timeout,
                                               retry_interval):
                return

            self._set_vm_state(instance,
                               os_win_const.HYPERV_VM_STATE_DISABLED)
        except os_win_exc.HyperVVMNotFoundException:
            # The manager can call the stop API after receiving instance
            # power off events. If this is triggered when the instance
            # is being deleted, it might attempt to power off an unexisting
            # instance. We'll just pass in this case.
            LOG.debug("Instance not found. Skipping power off",
                      instance=instance)

    def power_on(self, instance, block_device_info=None):
        """Power on the specified instance."""
        LOG.debug("Power on instance", instance=instance)

        if block_device_info:
            self._volumeops.fix_instance_volume_disk_paths(instance.name,
                                                           block_device_info)

        self._set_vm_state(instance, os_win_const.HYPERV_VM_STATE_ENABLED)

    def _set_vm_state(self, instance, req_state):
        instance_name = instance.name

        try:
            self._vmutils.set_vm_state(instance_name, req_state)

            LOG.debug("Successfully changed state of VM %(instance_name)s"
                      " to: %(req_state)s", {'instance_name': instance_name,
                                             'req_state': req_state})
        except Exception:
            with excutils.save_and_reraise_exception():
                LOG.error(_LE("Failed to change vm state of %(instance_name)s"
                              " to %(req_state)s"),
                          {'instance_name': instance_name,
                           'req_state': req_state})

    def _get_vm_state(self, instance_name):
        summary_info = self._vmutils.get_vm_summary_info(instance_name)
        return summary_info['EnabledState']

    def _wait_for_power_off(self, instance_name, time_limit):
        """Waiting for a VM to be in a disabled state.

           :return: True if the instance is shutdown within time_limit,
                    False otherwise.
        """

        desired_vm_states = [os_win_const.HYPERV_VM_STATE_DISABLED]

        def _check_vm_status(instance_name):
            if self._get_vm_state(instance_name) in desired_vm_states:
                raise loopingcall.LoopingCallDone()

        periodic_call = loopingcall.FixedIntervalLoopingCall(_check_vm_status,
                                                             instance_name)

        try:
            # add a timeout to the periodic call.
            periodic_call.start(interval=SHUTDOWN_TIME_INCREMENT)
            etimeout.with_timeout(time_limit, periodic_call.wait)
        except etimeout.Timeout:
            # VM did not shutdown in the expected time_limit.
            return False
        finally:
            # stop the periodic call, in case of exceptions or Timeout.
            periodic_call.stop()

        return True

    def resume_state_on_host_boot(self, context, instance, network_info,
                                  block_device_info=None):
        """Resume guest state when a host is booted."""
        self.power_on(instance, block_device_info)

    def _create_vm_com_port_pipes(self, instance, serial_ports):
        for port_number, port_type in serial_ports.items():
            pipe_path = r'\\.\pipe\%s_%s' % (instance.uuid, port_type)
            self._vmutils.set_vm_serial_port_connection(
                instance.name, port_number, pipe_path)

    def copy_vm_dvd_disks(self, vm_name, dest_host):
        dvd_disk_paths = self._vmutils.get_vm_dvd_disk_paths(vm_name)
        dest_path = self._pathutils.get_instance_dir(
            vm_name, remote_server=dest_host)
        for path in dvd_disk_paths:
            self._pathutils.copyfile(path, dest_path)

    def _check_hotplug_available(self, instance):
        """Check whether attaching an interface is possible for the given
        instance.

        :returns: True if attaching / detaching interfaces is possible for the
                  given instance.
        """
        vm_state = self._get_vm_state(instance.name)
        if vm_state == os_win_const.HYPERV_VM_STATE_DISABLED:
            # can attach / detach interface to stopped VMs.
            return True

        if not self._hostutils.check_min_windows_version(10, 0):
            # TODO(claudiub): add set log level to error after string freeze.
            LOG.debug("vNIC hot plugging is supported only in newer "
                      "versions than Windows Hyper-V / Server 2012 R2.")
            return False

        if (self._vmutils.get_vm_generation(instance.name) ==
                constants.VM_GEN_1):
            # TODO(claudiub): add set log level to error after string freeze.
            LOG.debug("Cannot hot plug vNIC to a first generation VM.",
                      instance=instance)
            return False

        return True

    def attach_interface(self, instance, vif):
        if not self._check_hotplug_available(instance):
            raise exception.InterfaceAttachFailed(instance_uuid=instance.uuid)

        LOG.debug('Attaching vif: %s', vif['id'], instance=instance)
        self._vmutils.create_nic(instance.name, vif['id'], vif['address'])
        self._vif_driver.plug(instance, vif)

    def detach_interface(self, instance, vif):
        try:
            if not self._check_hotplug_available(instance):
                raise exception.InterfaceDetachFailed(
                    instance_uuid=instance.uuid)

            LOG.debug('Detaching vif: %s', vif['id'], instance=instance)
            self._vif_driver.unplug(instance, vif)
            self._vmutils.destroy_nic(instance.name, vif['id'])
        except os_win_exc.HyperVVMNotFoundException:
            # TODO(claudiub): add set log level to error after string freeze.
            LOG.debug("Instance not found during detach interface. It "
                      "might have been destroyed beforehand.",
                      instance=instance)
            raise exception.InterfaceDetachFailed(instance_uuid=instance.uuid)

    def rescue_instance(self, context, instance, network_info, image_meta,
                        rescue_password):
        try:
            self._rescue_instance(context, instance, network_info,
                                  image_meta, rescue_password)
        except Exception as exc:
            with excutils.save_and_reraise_exception():
                err_msg = _LE("Instance rescue failed. Exception: %(exc)s. "
                              "Attempting to unrescue the instance.")
                LOG.error(err_msg, {'exc': exc}, instance=instance)
                self.unrescue_instance(instance)

    def _rescue_instance(self, context, instance, network_info, image_meta,
                         rescue_password):
        rescue_image_id = image_meta.id or instance.image_ref
        rescue_vhd_path = self._create_root_vhd(
            context, instance, rescue_image_id=rescue_image_id)

        rescue_vm_gen = self.get_image_vm_generation(instance.uuid,
                                                     image_meta)
        vm_gen = self._vmutils.get_vm_generation(instance.name)
        if rescue_vm_gen != vm_gen:
            err_msg = _('The requested rescue image requires a different VM '
                        'generation than the actual rescued instance. '
                        'Rescue image VM generation: %(rescue_vm_gen)s. '
                        'Rescued instance VM generation: %(vm_gen)s.') % dict(
                            rescue_vm_gen=rescue_vm_gen,
                            vm_gen=vm_gen)
            raise exception.ImageUnacceptable(reason=err_msg,
                                              image_id=rescue_image_id)

        root_vhd_path = self._pathutils.lookup_root_vhd_path(instance.name)
        if not root_vhd_path:
            err_msg = _('Instance root disk image could not be found. '
                        'Rescuing instances booted from volume is '
                        'not supported.')
            raise exception.InstanceNotRescuable(reason=err_msg,
                                                 instance_id=instance.uuid)

        controller_type = VM_GENERATIONS_CONTROLLER_TYPES[vm_gen]

        self._vmutils.detach_vm_disk(instance.name, root_vhd_path,
                                     is_physical=False)
        self._attach_drive(instance.name, rescue_vhd_path, 0,
                           self._ROOT_DISK_CTRL_ADDR, controller_type)
        self._vmutils.attach_scsi_drive(instance.name, root_vhd_path,
                                        drive_type=constants.DISK)

        if configdrive.required_by(instance):
            self._detach_config_drive(instance.name)
            rescue_configdrive_path = self._create_config_drive(
                context,
                instance,
                injected_files=None,
                admin_password=rescue_password,
                network_info=network_info,
                rescue=True)
            self.attach_config_drive(instance, rescue_configdrive_path,
                                     vm_gen)

        self.power_on(instance)

    def unrescue_instance(self, instance):
        self.power_off(instance)

        root_vhd_path = self._pathutils.lookup_root_vhd_path(instance.name)
        rescue_vhd_path = self._pathutils.lookup_root_vhd_path(instance.name,
                                                               rescue=True)

        if (instance.vm_state == vm_states.RESCUED and
                not (rescue_vhd_path and root_vhd_path)):
            err_msg = _('Missing instance root and/or rescue image. '
                        'The instance cannot be unrescued.')
            raise exception.InstanceNotRescuable(reason=err_msg,
                                                 instance_id=instance.uuid)

        vm_gen = self._vmutils.get_vm_generation(instance.name)
        controller_type = VM_GENERATIONS_CONTROLLER_TYPES[vm_gen]

        self._vmutils.detach_vm_disk(instance.name, root_vhd_path,
                                     is_physical=False)
        if rescue_vhd_path:
            self._vmutils.detach_vm_disk(instance.name, rescue_vhd_path,
                                         is_physical=False)
            fileutils.delete_if_exists(rescue_vhd_path)
        self._attach_drive(instance.name, root_vhd_path, 0,
                           self._ROOT_DISK_CTRL_ADDR, controller_type)

        self._detach_config_drive(instance.name, rescue=True, delete=True)

        # Reattach the configdrive, if exists and not already attached.
        configdrive_path = self._pathutils.lookup_configdrive_path(
            instance.name)
        if configdrive_path and not self._vmutils.is_disk_attached(
                configdrive_path, is_physical=False):
            self.attach_config_drive(instance, configdrive_path, vm_gen)

        self.power_on(instance)